1. Field the Invention
The present invention relates generally to ion membrane flow cell batteries for generating electrical potential. More particularly the present invention involves rechargeable batteries wherein membrane potentials generated by ions moving across ion membranes located in a stacked series of ion membrane flow cells are converted to electrical current and voltage by a single electrode pair.
2. Description of Related Art
Batteries which provide electrical voltage for utility load leveling and powering electric vehicles and spacecraft instrumentation have been the subject of intensive research for decades. In particular, efforts have been directed toward providing batteries having higher energy densities and higher power densities. Increased battery energy density contributes to increased vehicle driving range between battery recharging. On the other hand, increased power density provides improved vehicle acceleration and high speed driving. Thus, batteries used to power drive train motors are benefitted by high energy densities and power densities.
Electric vehicles and other drive train motors currently in use typically are powered by lead-acid batteries. One problem associated with these batteries is their limited cycle life when used under deep discharge conditions. Further, since the structural components of these batteries are metal, they are prone to corrosion. Also, the metal contained in the lead-acid voltage generating system contributes to high battery weights.
Additionally, lead-acid batteries contain numerous cells and incorporate an electrode pair for each cell. For many applications, multi-cell batteries having an electrode pair for each cell are needed to generate the power and current densities required for powering, for example, electric vehicles.
A significant problem associated with multi-cell batteries is that provision must be made for the conduction of electric current from one cell to the next. In lead-acid batteries, substantial amounts of lead are provided solely for current conduction. This lead contributes substantial weight and does not contribute useful energy. An additional problem associated with battery electrodes involves activation polarization, a voltage loss due to the process of changing electronic flow into ionic flow. Unfortunately, since multi-cell batteries have numerous electrode pairs, they exhibit substantial amounts of activation polarization and decreased cycle lives. The presence of numerous electrode pairs also contributes to decreased battery efficiency, decreased power density and decreased current density.
It would be desirable to provide a battery in which multiple, heavy internal current conductors are not needed. It would also be desirable to provide corrosion resistant batteries which exhibit decreased amounts of activation polarization. Further, it would be desirable to provide batteries having increased cycle lives while being capable of developing power densities and energy densities sufficiently high to power vehicles having acceptable acceleration, high speed and range.